var argvArr=process.argv;
if(argvArr[2]==undefined || argvArr[2]=='--help' || argvArr[2]=='-h'){
    console.log("命令行参数为一个数学表达式");
}else{
    try{
        console.log(eval(argvArr[2]));
    }catch(error){
        console.log(error);
    }
}
